Field
The technology of the disclosure relates to methods of preparing a demarcation of a fiber optic cable for inhibiting longitudinal movement of an optical fiber along with connectorized fiber optic cable assemblies.
Technical Background
Optical fiber is increasingly being used for a variety of applications including but not limited to broadband voice video and data transmission. Benefits of optical fiber use include extremely wide bandwidth and low noise operation. With the increasing and varied use of optical fibers it is important to provide reliable methods of interconnecting optical fibers. Fiber optic connectors have been developed for this purpose. It is important that fiber optic connectors not significantly attenuate or alter the transmitted signal. In addition, the fiber optic connector should be relatively rugged and configured to be connected and disconnected a number of times in order to accommodate changes in the optical fiber transmission path. The fiber optic cable should be reliably attached to the fiber optic connector. In this manner, the optical fiber should also be configured for its environment. For example, outdoor interconnections may require a more rugged fiber optic connector than those designed for indoor interconnections. Because of the skill and equipment required for making optical fiber connections in the field, fiber optic cables are often pre-connectorized with fiber optic connectors for plug and play connectivity.
In this manner, as shown in FIG. 1A, a conventional optical fiber 10 of a conventional fiber optic cable 12 may be inserted into a fiber optic connector 14 represented by a ferrule 16 held by a ferrule holder 18. The fiber optic cable 12 may include strength members 19(1), 19(2) to secure the fiber optic cable 12 to the fiber optic connector 14 as shown in FIG. 1B. The ferrule 16 may include a ferrule bore 20, within which the optical fiber 10 may be bonded with a bonding agent 22, for example, epoxy. The bonding agent 22 may hold an end portion 24 of the optical fiber 10 at an end face 26 of the ferrule 16 where the end portion 24 may establish an optical connection with a complementary end portion (not shown) of another optical fiber.
In order to ensure there is good contact between the end face 26 of the ferrule 16 and a complementary end portion, the ferrule 16 may be spring loaded with a spring 28 providing a spring force FS and thereby the ferrule 16 may move a longitudinal distance D1 within a housing assembly 29 of the fiber optic connector 14. The housing assembly 29 may be stationary when the optical connection is established between the end portion 24 of the optical fiber 10 and the complementary end portion (not shown). The fiber optic connector 14 includes a passage 30 where the optical fiber 10 may be accommodated while the ferrule 16 moves the longitudinal distance D1 as the fiber optic connector 14 may be optically connected and disconnected during use.
The fiber optic cable 12 may be secured to the housing assembly 29 by disposing the strength members 19(1), 19(2) between a crimp band 32 and a portion 34 of the housing assembly 29. A heat shrink 36 merely inhibits contaminants from entering the fiber optic connector 14 and is not a structural member securing the fiber optic cable 12 longitudinally to the housing assembly 29 of the fiber optic connector 14.
FIG. 1C depicts a mechanical schematic drawing of the mechanical attachments between the fiber optic cable 12 and the fiber optic connector 14 of FIG. 1B. As shown in FIG. 1C, the fiber optic cable 12 may include the optical fiber 10, strength members 19(1), 19(2), and outer jacket 38. The optical fiber 10, strength members 19(1), 19(2), and the outer jacket 38 may move relative to each other. The optical fiber 10 may be attached to the ferrule 16, which may be partially constrained by the housing assembly 29 and may generally move the distance D1 relative to the housing assembly 29 in a direction parallel to an optical axis A0. The strength members 19(1), 19(2) may be constrained to the housing assembly 29 at the crimp band 32. The outer jacket 38 of the fiber optic cable 12 is not secured to the housing assembly 29, but may move longitudinally away from the housing assembly 29.
As the fiber optic cable 12 may be exposed to mechanical bends and thermal cycles, the optical fiber 10 may move a longitudinal distance D2 relative to the strength members 19(1), 19(2) of the fiber optic cable 12. The longitudinal distance D2 movement, also known as “pistoning,” may be made possible because of excess fiber length or “EFL” where the fiber optic cable 12 is provided with excess longitudinal length of the optical fiber 10. The EFL may propagate along a length of the fiber optic cable 12 in either direction and thereby cause issues related to optical attenuation.
One potential issue is that the optical fiber 10 may be damaged by sharp bends known as “buckling” when the EFL enters the fiber optic connector causing the movement D2 in the fiber optic connector. For example, a sharp bend may be created in the passage 30 of the fiber optic connector 14. The sharp bend may cause damage to the optical fiber 10 and/or optical attenuation. Another issue may occur if the optical fiber 10 moves the longitudinal distance D2 away from the ferrule 16, and thereby attempts to move the optical fiber 10 away from the ferrule 10, then a tensile force may be created by the optical fiber 10 on the ferrule 16. The tensile force may damage the optical fiber 10 and/or cause optical attenuation. The tensile force may also overcome the spring force FS which may be only, for example, one (1) to two (2) pounds, to inadvertently disconnect the end portion 24 of the optical fiber 10 from the complementary end portion (not shown) of another optical fiber to thereby optically decouple the fiber optic connector 14, and thereby disable the signal being transmitted through the fiber optic connector 14.
A fiber optic connection is needed that is more resistant to mechanical and thermal changes in the fiber optic cable that can cause tensile forces or buckling of the optical fiber 10 in the fiber optic connector. In this manner, the optical fiber may be less likely to be damaged or inadvertently disconnected, and optical attenuation may be inhibited.